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determined by the status of the internal clock and the internal
schedules.
OCCUPIED / UNOCCUPIED / MORNING WARM-UP
OCCUPIED
In Occupied mode, all installed options enabled by the
parameter settings are available. The supply fan is operated
[controlled to the duct pressure setpoint if a VAV], optional unit
heating is available at full capacity, the optional power exhaust
system is enabled, the economizer outside air dampers go to
their minimum position or open for free cooling. This operation
continues until the unit enters Unoccupied mode. When the
control sees an Occupied override button push from the
thermostat or space sensor, it will go to Occupied mode for the
length of time set in the parameters, up to four hours. If the unit
is in Space Sensor operation, the fan will operate at full speed
[controlled to the duct pressure setpoint if a VAV].
A VAV standalone unit will run MWUP the first hour of the OCC
override signal, then go to Occupied. The supply fan will run
continuously.
UNOCCUPIED
In Unoccupied mode, the economizer goes to full closed; the
supply fan will only operate if there is a call for heating or
cooling [controlled to the duct pressure setpoint if a VAV]. If
heating is required, all installed stages will be energized.
The bypass VFD is a standard Variable Frequency
Drive packaged with a further set of contactors When
bypass mode is activated, contactors route power
around the VFD, connecting the indoor fan motor
direct to supply voltage. At this point the motor will go
to full RPM regardless of the duct pressure signal,
because the VFD is out of the loop, and there is a
potential for over pressuring the ducts.
The air balancer must set maximum duct static / CFM
to stay within a static pressure that the ductwork of that
installation can tolerate when the motor is at full RPM,
considering that the VAV boxes, if they are part of the
system, may not be full open.
If the duct system includes VAV boxes, they must be
driven open in Bypass mode in the same manner as
going to heat mode. The drive indicates being in "bypass"
mode with normally open contacts wired to terminal block
1, position 5 and 6 across Danfoss relay M3 [refer to
drawings supplied by Danfoss, packed with the unit].
Voltage sufficient to signal the boxes to open must be
wired through this contact. This is a field-install
connection.
Johnson Controls Unitary Products
MORNING WARM-UP [MWUP]
The unit enters a morning warm-up mode going in to the first
Occupied period of the control's internal daily schedule. In this
mode, the supply fan is operated at full volume, optional unit
heating is engaged at full capacity if needed, the optional power
exhaust system is enabled, the economizer outside air dampers
close (return air dampers open), cooling is disabled, and
voltage is provided at H1 to signal the remote VAV boxes to
open. This operation continues until the return air temperature
exceeds the adjustable setpoint of the Morning Warm-up bulb
thermostat (MWUP).
The parameter for MWUP must be turned on. Without Intelli-
Start, MWUP will start one hour ahead of Occupied. Cooling will
not start until the Occupied mode starts. In MWUP, the control
will operate the fan and energize heat after monitoring RAT five
minutes after going into MWUP, or if RAT goes two degrees
below the MWUP setpoint.
UNIT CONTROLS
1.
The control reviews parameters, the unit clock, and occupied /
Holiday schedules to select the appropriate mode. In Occu-
pied mode, the unit will look at inputs enabled by parameter
settings. It will default to secondary inputs if necessary.
When the unit is running in Occupied mode, the duct pres-
sure controller, if that option is installed, is activated; the
optional power exhaust system is activated, power is
applied to the airflow proving switch (APS), and to the sup-
ply fan motor contactor (5M) to engage the supply fan. If
the supply fan operates correctly (proper rotation) the pres-
sure difference between the supply fan section and the
heating section increases and APS closes to enable opera-
tion. The control waits 90 seconds for the fan to reach equi-
librium, then looks at the APS.
For units without optional head pressure control: If the out-
side air temperature rises above 50 °F the control enables
all mechanical cooling stages. If the outside air tempera-
ture falls below 40 °F, then all mechanical cooling stages
are locked out.
For units with head pressure control: Enable third and
fourth (40 Ton only) stage mechanical cooling when the
ambient temperature rises above 50 °F. If the outside air
temperature falls below 40 °F, mechanical cooling stages 3
and 4 (40 Ton only (all R410a)) are locked out. Enable first
and second stage mechanical cooling when the ambient
temperature rises above 10 °F. If the outside air tempera-
ture falls below 0 °F, all mechanical cooling stages are
locked out.
2.
While the return air temperature remains below the set-
point of MWUP (Morning Warm-up), engage the unit heat
(optional) at full capacity.
For Inlet Guide Vane VAV: terminal VFD provides a 10VDC
signal for the actuator, thus forcing the inlet guide vane
dampers to fully open during the warm-up cycle. Terminal
H1, heat stage 1, is used to signal the remote VAV boxes to
open. In this warm-up mode, VAV and the economizer
351579-YTS-B-0608
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